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Bulletin 3 

Structural Materials Research Laboratory 

Lewis In st itu te 

Chicago 



Effect of Vibration, Jigging 

and Pressure on Fresh 

Concrete 

By 

DUFF A. ABRAMS 

Professor in Charge of Laboratory 



(Authorized Reprint from the Copyrighted Proceedings of the 
American Concrete Institute, Vol. XV, 1919) 



Published by the 

STRUCTURAL MATERIALS RESEARCH LABORATORY 

Second Printing, September, 1922 



**K»i}nM» 



"DESEAECHES in the properties of concrete and concrete mate- 
-"* rials at the Structural Materials Kesearch Laboratory are being 
carried out through the cooperation of the Lewis Institute and the 
Portland Cement Association, Chicago. The research work has been 
under way since September 1, 1914. 

The control of the policies of the Laboratory is vested in an 
Advisory Committee, consisting of representatives of the Lewis 
Institute and the Portland Cement Association, as follows : 

Lewis Institute : 
GEO. N. CARMAN, Director of Lewis Institute. 
DUFF A. ABRAMS, Professor in Charge of Laboratory. 

Portland Cement Association : 
F. W. KELLEY, Chairman, Technical Problems Committee, Albany, N.Y. 
ERNEST ASHTON, Member, Technical Problems Committee, Allen- 
town, Pa. 

The investigations are being carried out by a staff of engineers, 
chemists, and assistants who give their entire time to this work. The 
results of these researches are published in the form of papers before 
engineering and technical societies and in Circulars and Bulletins 
issued by the Laboratory. 



Bulletin 3 

Structural Materials Research Laboratory 

Lewis Institute 

Chicago 



Effect of Vibration, Jigging 

and Pressure on Fresh 

Concrete 



By 

DUFF A? ABRAMS 

Professor in Charge of Laboratory 



(Authorized Reprint from the Copyrighted Proceedings of the 
American Concrete Institute, Vol. XV, 1919) 



Published by the 

STRUCTURAL MATERIALS RESEARCH LABORATORY 

Second Printing, September, 1922 



p 



0< 



<s 






FOREWORD 



This report was originally published in the Proceedings of the 
American Concrete Institute, Vol. XV, 1919; it was reprinted as 
Bulletin 3 of this Laboratory, November, 1919. 

In this second printing, a few footnotes have been added 
which show deviations of present practice from that followed in 
these tests. 

There has been a marked increase in the use of vibrating- and 
jigging equipment during the past three years, especially in prod- 
ucts plants. 

For the assistance of those who may wish to look up earlier 
work on the subject, a brief list of references has been added. 



EFFECT OF VIBRATION, JIGGING AND PRESSURE 
ON FRESH CONCEETE. 

By Duff A. Abrams. 

Introduction. 

An experimental study of the effect of vibration and pressure on fresh 
concrete on its strength and other properties is of interest in view of the 
frequent use of such devices as hand-hammering of forms, or air-hammer- 
ing, jigging or vibration as an aid in placing concrete. Such methods are 
particularly applicable to the construction of reinforced-concrete ships and 
houses, where thin sections and a multiplicity of reinforcing members are 
of common occurrence. Jigging or vibrating machines are frequently used 
in concrete products plants. The effect of pressure on fresh concrete is of 
interest in certain problems of concrete design. 

Little attention has heretofore been given to the experimental study of 
the effects produced by vibration and jigging fresh concrete. A few tests 
were made in a study of the effect of pressure on fresh cement paste in a 
confined space by James E. Howard, at Watertown Arsenal. 1 The effect of 
pressure on the compressive strength and bond was studied by the writer 
at the University of Illinois in 1913. 2 Since the tests reported herein were 
completed, Prof. F. P. McKibben has published a report on compression 
tests of concrete columns which set under pressure. 3 

The tests included in this report were made as a part of the experi- 
mental studies of concrete and concrete materials being carried out through 
the cooperation of Lewi's Institute and the Portland Cement Association. 

Outline of Tests. 
The tests included in this report cover the following topics : 

1. Different methods of hand-molding of test cylinders. 

(a) Puddling with f-in. round steel bar (varying number of 
strokes). 

(b) Tamping (tampers of different size). 

(c) Tapping metaLforms after puddling. 

2. Effect of vibrating fresh concrete (small electric motor, Fig. 1.) 

(a) Time of vibration varied up to 1 min. 

3. Effect of jigging fresh concrete (using machine shown in Fig. 2). 

(a) Concrete of different mixes (1:7 to 1:3). 

(b) Concrete of different relative consistencies (0.70 to 1.25). 



1 Cement Age, June, 1905. 

2 "Tests of Bond between Concrete and Steel." Bulletin 71, 111. Engineering 
Experiment Station, 1914. 

3 Eng. News-Rec, Dec. 5, 1918. 



I Structural Materials Research Laboratory. 

(c) Using aggregate of different grading (fineness modulus 4.00 
to 6.50). 

(d) Using aggregate of different sizes (0-28 sand to 0-1^-in. 
concrete aggregate). 

(e) Using coarse aggregate of different' shape (pebbles and 
crushed stone). 

(/) Effect of rate of jigging (0 to 150 r. p. m.). 
(g) Effect of height of drop (0 to 0.50 in.). 
(h) Effect of length of time jigged (up to 3 min.) 
(i) Effect of age of concrete before jigging (up to 6 hr.). 
(/) Jigged with 30-lb. weight on top of fresh concrete. 
(k) Hand puddling on jigging machine while in operation. 
4. Effect of pressure on fresh concrete (method of applying the 
higher pressures shown in Fig. 3). 

(a) Using different pressures (0 to 500 lb. per sq. in.).' 

(b) Effect of duration of pressure (15 min. to 16 hr.). 

(c) Effect of removal of water by pressure. 

This series included 900 compression tests of 6 by 12-in. concrete 
cylinders at the age of 28 days. All specimens were made from the same 
materials at the same time, consequently direct comparisons may be made 
between any two sets of tests. 

Materials. 

The portland cement used consisted of a mixture of equal parts of 
four brands purchased from Chicago dealers. The cement conformed to 
all the requirements of the Standard Specifications and Tests for Portland 
Cement of the American Society for Testing Materials. 

In general the aggregates consisted of sand and pebbles from the 
Chicago Gravel Company's pit near Elgin, 111. In one group of tests 
crushed limestone was used as coarse aggregate. Sieve analysis and 
miscellaneous tests of aggregates are given in Table 1. 

The "fineness modulus" of an aggregate may be used as a measure of 
its size and grading. It is the sum of the percentages in the sieve analysis 
divided by 100. The sieve analysis is expressed in terms of weight or 
volume coarser than each sieve. Tyler standard screen scale sieves are 
used. The sizes of sieves and fineness moduli of the aggregates used in 
these tests are shown in Table 1. Low values of fineness modulus corre- 
spond to the small size and high values to the coarse sizes of the ag- 
gregate.* 

Test Pieces; 

All test pieces consisted of 6 by 12-in. cylinders which were stored in 
damp sand for 28 days. The concrete for each specimen was propor- 
tioned separately and mixed by hand with a bricklayer's trowel in a 
shallow metal pan. The forms consisted of 12-in. lengths of cold-drawn 



*For further details on fineness modulus of aggregates see the writer's report on 
"Design of Concrete Mixtures," Bulletin 1, Structural Materials Research Laboratory. 



Effkct of Vibration, Jigging and Pressure on Concrete. 



steel tubing, split along one element. Each form stood on a machined 
cast-iron base plate. A smooth top was formed by means of neat cement 
and plate glass. 

Unless otherwise noted, the specimens were molded by the "standard" 
hand-puddling method before subjecting them to vibration, jigging or 
pressure. This method consists of puddling the fresh concrete in the 
metal form in 4-in. layers by means of 25 strokes with a ^-in. round 
steel bar and leveling off with a trowel. This method has been in use for 

Table 1. — Miscellaneous Tests of Aggregates. 







Weight 
lb. per 




Sieve Analysis 


of Aggregate 




Fineness 


Size 


Kind 


Density 


(Per cent by weight coarser 


than each sieve 


.) 


Modu- 






cu. ft. 














lus.** 






























100 


48* 


28* 


14* 


8 


4 


fin. 


fin. 


1§ in. 




0-28* 




102 


0.61 


88 


42 

















1.20 


0-14* 


Elgin 


104 


0.62 


90 


91 


36 















2.25 • 


0-8 


Sand 


108 


0.65 


99 


93 


50 


22 













2.64 


0-4 


and 


112 


0.67 


99 


94 


59 


36 


18 











3.06 


0-1 in. 


Pebbles 


120 


0.72 


99 


96 


73 


57 


46 


33 


'6 






4.04 


0-f in. 




124 


0.74 


99 


97 


82 


72 


64 


58 


30 







5.02 


0-H in. 


) 


128 


0.77 


99 


98 


87 


80 


75 


68 


48 


20 





5.75 






119 


0.71 


99 


95 


69 


51 


38 


24 


17 


7 





4.00 




f Elgin 


125 


0.75 


99 


97 


79 


68 


58 


49 


35 


15 





5.00 


0-H in. 


Sand 


126 


0.76 


99 


98 


85 


76 


69 


62 


43 


18 





5.50 


and 


128 


0.77 


99 


98 


87 


80 


75 


68 


48 


20 





5.75 




1 Pebbles 


128 


0.77 


100 


98 


90 


84 


79 


75 


52 


22 





6.00 






125 


0.75 


100 


99 


92 


88 


84 


81 


57 


24 





6.25 






120 


0.72 


100 


99 


95 


92 


90 


87 


62 


25 





6.50 






123 


0.74 


99 


95 


69 


51 


38 


24 


17 


7 





4.00 




Elgin 


128 


0.77 


99 


97 


79 


68 


58 


49 


35 


15 





5.00 




Sand 


124 


0.74 


99 


98 


85 


76 


69 


62 


43 


18 





5.50 


0-H in. 


and 


122 


0.73 


99 


98 


87 


80 


75 


68 


48 


20 





5.75 




Crushed 


118 


0.71 


100 


98 


90 


84 


79 


75 


52 


22 





6.00 




Lime- 


114 


0.68 


100 


99 


92 


88 


84 


81 


57 


24 





6.25 




stone 


110 


0.66 


100 


99 


95 


92 


90 


87 


62 


25 





6.50 



*(Note added at Second Printing, September, 1922.) The No. 48, 28, and 14-mesh sieves give the same 
separation as the No. 50, 30, and 16 now used in the "Tentative Method of Test for bieve Analysis of 
Aggregates for Concrete" of the American Society for Testing Materials. The No. 50, 30, and 16 sieves are 
now used in all our tests. 

**The sum of percentages in sieve analysis, divided by 100. 

several years in our research work and has been found to give uniform 
results for different operators. The strength of the concrete produced by 
this method of molding is used as a basis for comparison (100 per cent) 
for all other methods of treatment included in this investigation. 

The mixture is expressed as one volume of cement to a given number 
of volumes of mixed aggregate. A 1 : 5 mix expressed in this manner is 
about the same as the ordinary 1:2:4 mix. The exact equivalent of the 
latter will vary with the size and grading of the aggregates. 

The water content of the concrete is expressed in terms of the rela- 
tive consistency and the "water-ratio." A relative consistency of 1.00 
(normal consistency) is of such plasticity that the concrete of usual 
mixes will give a slump of ^ to 1 in. if the metal form is withdrawn by a 



4 Structural Materials Research Laboratory. 

steady upward pull immediately after molding the cylinderf by the standard 
method. A relative consistency of 1.10 contains 10 per cent more water 
than normal consistency. The water-ratio is the ratio of volume of water 
to volume of cement in the batch. The weight of cement was assumed 
as 94 lb. per cu. ft. For one mix and given concrete materials the relative 
consistency and water-ratio may be used interchangeably. 




FIG. 1.— ELECTRIC VIBRATOR. 

Shows set-up for vibration tests given in Table 3. 
Motor weighed 12 lb., ran about 1000 r. p. m. 

In the hand-molded specimens the method of placing the concrete was 
varied by changing the number of strokes of the puddling bar, using layers 
of different thickness, etc. Hand-tampers 2 in. and 5 in. in diameter were 
also used. In one set of tests the form was struck with a steel bar after 
molding by the standard puddling method. 

ffNote added at Second Printing, September 1922.) Present practice in making the slump test for con- 
sistency or workability of concrete requires the use of a 4 by 8 by 12-in. truncated cone. For concrete of a given 
consistency the cone gives slumps about % less than the cylinder. The truncated cone is specified in the Prog- 
ress Report of the Joint Committee on Standard Sp3cifications for Concrete and Reinforced Concrete and is 
used in the Tentative Specifications for Workability of Concrete for Concrete Pavements of the American 
Society for Testing Materials. 



Effect of Vibration, Jigging and Pressure on Concrete. 5 

In the vibration tests the cylinder mold was bolted to a light timber 
table and the concrete specimen molded by the standard hand-puddling 
method described above. 

Violent vibration was produced by holding an electric motor frame 
against the side of the steel form as shown in Fig. 1. The -motor carried 
an eccentric flywheel, weighed 12 lb. and ran about 1000 r. p. m. The time 
of vibration varied from 5 sec. to 1 min. 

The jigging tests were made on the machine shown in Fig. 2. The 
machine consisted of a framework carrying a metal table about 4 ft. wide 




FIG 2.— JIGGING MACHINE. 

Steel table 4 by 8 ft.; weight 700 lb. Table raised by means of cams; rate and 
height of drop can be varied over wide range. 

and 8 ft. long weighing about 700 lb. The table was raised by means of 
belt-driven cams on two longitudinal shafts. The rate and height of drop 
could be varied over a wide range. In most of the tests the machine was 
run for 20 sec. at 100 drops per min., 0.1-in. drop; however, each of these 
factors were varied with the other two constant. 

All specimens were molded by the standard hand-puddling, method 
before pressure was applied. Pressures up td 10 lb. per sq. in. were 
applied by piling weights on top of a loose-fitting cover plate. Pressures 
of 25 and 50 lb. per sq. in. were applied by weighted levers. Pressures of 
100 to 500 lb. per sq. in. were obtained by placing the freshly molded 
specimen in a testing machine, as shown in Fig. 3. The spring facilitated 
maintaining a constant pressure. For all pressures the time of applica- 
tion varied from 15 min. to 16 hr. 

The metal forms are fairly tight and permit little leakage of water 
under ordinary conditions. For the wetter concretes the joints were 
sealed with paraffin. In the pressure tests the water expelled was col- 
lected by means of sponges and weighed. It should be noted that this 
water was almost clear. 

Test cylinders were made in sets of 5 on different days. One speci- 
men of each form was made before starting the second round. The 
strengths given in the tables are the average of 5 entirely independent 



6 Structural Materials Research Laboratory. 

tests. In this way minor variations in materials, proportions, manipula- 
tion, etc., are eliminated. In the case of the "standard" hand-puddled 
specimens were made in different parts of the series. 




FIG. 3.— METHOD OF APPLYING PRESSURE TO 
FRESH CONCRETE. 

The higher pressures were applied by means of a test- 
ing machine. The spring facilitated maintaining a 
constant pressure. The plate in contact with fresh 
concrete was loose-fitting. The water expelled from 
concrete was collected by means of sponges and 
weighed. 



Test Data and Discussion. 

Data of the tests will be found in Tables 2 to 7. Only average values 
are reported. It will be noted that the "standard" hand-puddled concrete 
(average of 15 tests) is used as the basis of comparison. The diagrams 
in Figs. 4 to 16 give the data in graphical form. 

A comparison of the relative effects of puddling 1 : 5 plastic concrete 
with a steel bar and tamping with tampers of different weight and size 
is given in Table 2. 



Effect of Vibration, Jigging and Pressure on Concrete. 



Table 2. — Effect of Method of Molding Concrete Specimens. 

Compression tests of 6 by 12-in. cylinders. 

Mix 1 : 5 by volume. 

Relative consistency, 1.00; water ratio, 0.87. 

Age at test 28 days; stored in damp sand; tested damp. 

Aggregate — sand and pebbles from Elgin, 111., graded O-l^ in.; fineness modulus, 5.75. 

Each value is the average of 5 tests made on different days. 



Ref. No. 


Treatment of Concrete 


Compressive Strength 


lb. per 
sq. in. 


Per cent of 
Standard 


1 


12 strokes around perimeter of form for each 4-in. layer of concrete 
using f-in. steel bar. 


2680 


96 


31 
51 

84 


25 strokes distributed over section for each 4-in. layer using f-in. 
steel bar. (Standard method.) 


2800 
2710 
2840 

2780* 


[ 100 

1 
) 


2 


50 strokes distributed over section for each 4-in. layer using f-in. bar. 


2810 


101 


147 


12 strokes on each 3-in. layer using 2-lb. tamper 2 in. in diameter. 


2690 


97 


148 


12 strokes on each 6-in. layer, using 2-lb. 2-in. tamper. 


2420 


87 


149 


12 strokes on first 3-in. layer using 2-lb. 2-in. tamper, forms then 
filled before tamping again with 12 strokes. 


2430 


87 


150 


12 strokes on first 3-in. layer, using 2-lb. 2-in. tamper, remaining 
concrete settled by tapping form lightly. 


2500 


90 


3 


25 strokes distributed over section for each 4-in. layer with 2-lb. 
2-in. tamper. 


2800 


101 


4 


25 strokes distributed over section for each 4-in. layer with 2-lb. 
5-in. tamper. 


2570 


92 


5 


Standard method of molding, except form struck 3 light blows with 
steel bar after puddling each 4-in. layer. 


. 2740 


98 



*Average of 15 tests made on different days. This value is 
3, 6 and 7. 



a basis for comparison in Tables 2, 



The effect of vibration with electric vibrator is shown in Table 3 and 
Fig. 4. Vibrating for about 30 seconds caused no appreciable effect on the 
strength of concrete which had been puddled in place by hand. The tests 
indicate that hand-puddling (if thoroughly done) is just as effective as 
vibration in placing concrete. In other words, concrete which completely 
fills the form is not improved by vibration. This should not be construed 
as meaning that vibration is not effective in causing concrete to find its 
way into intricate form worlc and around the reinforcing bars. 

The effect of jigging is shown in Tables 4 to 6, and Fig. 5 to 12. The 
jigging method used was one which would be applicable to concrete prod- 
ucts plants. The tests show that in general jigging of concrete which 
has been placed by puddling is injurious to the strength. The improve- 
ment for the small-sized aggregates is probably due to the fact that the 
puddling method is not so satisfactory for this condition. 

In comparing the tests of crushed limestone and pebbles in Table 5 it 
should be noted that the three coarsest gradings in each group (fineness 



Structural Materials Research Laboratory. 



Table 3. — Effect of Vibration With Electric Motor. 

Method of vibrating shown in Fig. 1. 

Compression tests of 6 by 12-in. cylinders. 

Mix, 1:5 by volume. 

Age at test 28 days; stored in damp sand; tested damp. 

Aggregate — sand and pebbles from Elgin, 111., graded 0-U in.; fineness modulus, 5.75. 

Each value is the average of 5 tests made on different days. 

Results of tests are platted in Fig. 4. 



Ref. No. 




Compressive Strength 


Treatment of Concrete 


lb. per 
sq. in. 


Per cent of 
Standard 


31.51,84 


Standard method of molding. 


2780* 


100 


6 


Standard method of molding, vibrated 5 sec. 


2880 


104 


7 


Standard method of molding, vibrated 10 sec. 


2640 


95 


8 


Standard method of molding, vibrated 20 sec. 


2830 


102 


9 


Standard method of molding, vibrated 30 sec. 


2700 


97 


10 


Standard method of molding, vibrated 45 sec. 


2520 


91 


11 


Standard method of molding, vibrated 60 sec. 


2470 


89 



"Average of 15 tests made on different days, See Table 2. 



Si 
\ 

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% -' 

I 



t /ooo 



39ec/ 'or Mbno/rbs? 



/O <?0 JO 40 SO 

7Tme of V/braf /'on -seconds 



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FIG. 4.— EFFECT OF VIBRATION ON THE STRENGTH OF CONCRETE. 



Vibration produced by electric motor shown in Fig. 1. Compression tests of 
6 by 12-in. cylinders. Age, 28 days. Data from Table 3. 



Effect of Vibration, Jigging and Pressure on Concrete. 



Table 4. — Effect of Jigging on the Strength of Concrete. 



(Concrete of Different Mixes and Consistencies.) 



All cylinders were molded by the standard method bafore vibrating on machine shown in Fig. 2. 

(100 r.p.m.; 0.1-in. drop; jigged 20 sec.) 
Compression tests of 6 by 12-in. cylinders. 

Aggregates, sand and pebbles from Elgin, 111., graded 0-U-in.; fineness modulus, 5.75. 
Age at test 28 days; stored in damp sand: tested damp. 
Each value is the average of 5 tests made on different days. 
Values platted in Fig. 5. 











Compressive Strength 




Mix 


Relative 


Water- 








Ref 


by 

Vol. 


Consist- 


Ratio to 




Standard 


Jigged 


No. 


ency 


Volume of 


Standard Method 


Method Plus 


Concrete, 


Cement 


lb. per sq. in. 


Jigging, lb. per 


Per cent of 












sq. in. 


Standard 


75 


1:7 


0.70 


0.757 


1270 


1560 


123 


76 




0.80 


0.866 


1650 


1910 


116 


77 




0.90 


974 


1730 


2000 


116 


78 




1.00 


1.081 


1710 


1800 


105 


79 




1.10 


1.190 


1480 


1460 


99 


80 




1.25 


1.353 


1140 
Av. 1500 


1110 
1640 


97 
109 


81 


1:5 


0.70 


0.612 


1650 


2020 


122 


82 




0.80 


0.700 


2560 


2870 


112 


83 




0.90 


0.788 


2920 


3120 


107 


84 




1.00 


0.875 


2840 


2630 


93 


85 




1.10 


0.962 


2120 


2040 


96 


86 




1.25 


1.085 


1580 
Av. 2280 


1560 
2370 


99 
104 


87 


1:4 


0.70 


0.540 


1690 


2160 


128 


88 




0.80 


0.618 


3760 


3600 


96 


89 




0.90 


0.695 


3750 


3710 


99 


90 




1.00 


0.777 


3510 


3190 


91 


91 




1,10 


0.849 


2890 


2520 


87 


92 




1.25 


0.965 


1880 
Av. 2910 


1750 
2820 


93 
97 


93 


1:3 


0.70 


0.469 


2160 


2640 


122 


94 




0.80 


0.536 


4050 


4410 


109 


95 




0.90 


0.603 


4530 


4800 


106 


96 




1.00 


0.670 


4050 


3920 


97 


97 




1.10 


0.737 


3420 


3470 


101 


98 




1.25 


0.838 


2680 


2420 


90 








< 


Av. 3480 


3610 


104 



10 



Structural Materials Research Laboratory. 



Table 5.— Effect of Jigging on the Strength of Concrete. 
( Using Aggregates of Different Size and Grading.) 

Values from tests platted in Fig. 7 and 8. 

All cylinders were molded by the standard method before jigging on machine shown in Fig. 2. (100 r p m ■ 

0.1-in. drop; jigged 20 sec.) 
Compression tests of 6 by 12-in. cylinders. 
Age at test 28 days; stored in damp sand; tested damp. 
Aggregates— sand and pebbles from Elgin, 111., except where otherwise noted. 
Each value is the average of 5 tests made on different days. 
Vari TOk adinS ' n la3t tW ° gT ° UP3 Wa3 produC2d by mixin ? different percentages of sand and coarse 







Aggregate 


Relative 
Consist- 
ency 


Water- 
Ratio to 
Volume of 


Compressive Strength 


Ref. 

No. 


Mix 
by 
Vol. 


Size 


F m 


Standard Method 


Standard 
Method Plus 


Jigged 
Concrete, 










Cement 


lb. per sq. in. 


Jigging, lb. per 


Per cent of 
















sq. in. 


Standard 


123 
124 
125 
126 
127 
128 
84 


1:5 


0-28 
0-14 
0-8 
0-4 


1.20 
2.25 
2.64 
3.05 
4.04 
5.02 


1.00 


1.410 
1.290 
1.245 
1.195 
1.080 
0.960 


360 
510 
500 
950 
1540 
2290 


40Q 
580 
650 
1060 
1270 
2060 


111 
114 
130 
112 

82 
90 
93 




0-l| 


5.75 




0.875 


2840 


2630 


129 
130 
131 
132 
133 
134 
96 


1:3 


0-28 
0-14 
0-8 
0-4 

<H 

o-l 

0-li 


1.20 
2.25 
2.64 
3.06 
4.04 
5.02 
5.75 


1.00 
.... 


0.990 
0.920 
0.890 
0.860 
0.790 
0.720 
0,670 


680 
1060 
1520 
2080 
3050 
3840 
4050 


860 
1360 
1720 
2020 
2930 
3420 
3920 


126 
128 
113 
97 
96 
89 
97 


47 
48 
49 
50 
51 
52 
53 


1:5 


0-li 


4.00 
5.00 


1.00 


1.08) 
0.960 


1450 

2160 


1460 

1960 


101 
91 
90 
79 
97 
96 
95 






5.50 

5.75 

6.00t 

6.25f 

6.50f 




0.910 
0.875 
0.845 
0.810 
0.785 


2500 
2980 
2710 
2610 
2110 


2250 
2360 
2630 
2520 
2010 


54* 
55* 
56* 
57* 
58* 
59* 
60* 


1:5 

::: 

i 


o-H 


4.00 
5.00 
5.50 
5.75 
6.00f 
6.25f 
6.50f 


1.00 


1.085 
0.950 
0.910 
0.875 
0.845 
0.810 
0.785 


1180 
2030 
2450 
2630 
2420 
1960 
1550 


1390 
1850 
2290 
2430 
2500 
1760 
1460 


118 
91 
93 
92 

103 
90 
94 



k Crushed limestone for coarse aggregate 



Effect of Vibration, Jigging and Pressure on Concrete. 
Table 6. — Effect of Jigging on the Strength of Concrete. 

All cylin lor? were molded by the standard method before jigging on machine shown in Fig. 2. 

Compression test* of 6 by 12-in. cylinders. 

Age at test 28 days: stored in damp sand: tested damp. 

Aggregates— sand and psbblee from Elgin, 111. (graded 0-1 | in.). 

Each Va'ue is the avera.v of 5 tens made on different days. 



Ref. 



by 
^ olume 



P. M. 

of 
Aggre- 
gate 



Relative 
Consist- 
ency 



Water- 
Ratio 
to Volume 
of Cement 



Compressive 
Strength 



lb. per Per cent of 
sq. in. Standard 



Treatment of Concrete 



Effect of Height of Drop. 100 r.p.m.. for 20 sec. (See Fig. 9). 



31,51.84 


1:5 


5 . 75 


1.00 


0.875 


2780* 


100 


Standard method of molding. 


17 










2340 


84 


Drop .02 in. 


18 










2480 


89 


Drop .05 in. 


19 










2250 


81 


Drop .10 in. 


2D 










2520 


91 


Drop .20 in. 


21 










2640 


95 


Drop .30 in. 


■>-> 










2460 


88 


Drop .50 in. 



Effect of Rate of Jigging. 0.1-in. drop, for 20 sec. (See Fig. 10) 



31.51.84 


1:5 


5 . 75 


1.00 


0.875 


2780* 


100 


Standard method of molding. 


12 










2640 


95 


Jigged at 30 r.p.m. 


13 










2490 


90 


Jigged at 50 r.p.m. 


14 










2470 


89 


Jigged at 75 r.p.m. 


15 










2520 


91 


Jigged at 100 r.p.m. 


16 










2420 


87 


Jigged at 150 r.p.m. 



Effect of Time Ji ged at 100 r.p.m., 0.1-in. drop (See Fig. 11). 



13. 51, 84 


1:5 


5 . 75 


1.00 


0.875 


2780* 


100 


Standard method'of molding. 


32 












2440 


88 


Jigged for 5 sec. 


33 












2260 


81 


Jigged for 10 sec. 


34 












2390 


86 


Jigged for 20 sec. 


35 












2320 


83 


Jigged for 30 sec. 


36 












2251 


81 


Jigged for 45 sec. 


37 












2190 


79 


Jigged for 1 min. 


38 












2090 


75 


Jigsred for 2 min. 


39 












217J 


78 


Jigged for 3 min. 



Miscellaneous Jigging Tests, 100 r.p.m., 0.1-in. drop, j'gied 2"! sec. (See Fig. 12). 



51.51,84 


1:5 


5. 


"5 


1.00 


0.875 


2780* 


100 


40 










2780 


100 


5. 19. 34 










2390 


86 


41 














2550 


92 


42 














2940 


106 


43 














2950 


106 


44 














3000 


108 


45 














2870 


103 


46 














2770 


100 



Standard method of molding. 
Standard method of molding, 

jigged with 30-lb. weight on 

top. See Figs. 9. 10 and 11.) 
Jigged immediately. 
Stood 1 hr. before jigging. 
Stood 2 hr. before jigging. 
Stood 3 hr. before jigging. 
Stood 4 hr. before jigging. 
Stood 6 hr. before jigging. 
Molded by standard method 

on jigging machine while in 

operation. 



* Average of 15 tests made ondiJerent days. See Table 2 



12 



Structural Materials Research Laboratory. 



Table 7. — Effect of Pressure on the Strength of Concrete. 

All cylinders were molded by standard method b afore pressure was applied. Pressures higher than 
50 lb. per sq. in. were applied by a testing machine, as shown in Fig. 3. 



Ref. 
No. 



Mix 

by 

Volume 


F.M. 
of 

Agg. 


Relative 
Consist- 
ency 


Water-Ratio 


Compressive 

Strength 


As 
Mixed 


After 
Pressure 


lb. p 3 r 
sq. in. 


Per cent 
of Stand- 
ard 



Treatment of Concrete 



31,51,84 











Pressure Applied 1 


5 Minutes. 




31,51,84 


1:5 


5.75 


1.00 


0.875 


0.875 


2780* 


100 


Standard method of molding 


23 










0.842 


3140 


113 


Pressure, 2 lb. par sq. in. 


24 










0.845 


3000 


108 


5 lb. par sq. in. 


25 










0.831 


2930 


105 


" 10 lb. par sq. in. 


26 










0.816 


2900 


104 


" 25 lb. par sq. in. 


27 










0.820 


3130 


113 


" 50 lb. per sq. in. 


28 










0.810 


3470 


125 


100 lb. per sq. in. 


29 










0.785 


3360 


121 


200 lb. par sq. in. 


30 








Av. 


0.751 
0.819 


3590 
3150 


129 
113 


" 500 lb. par sq. in. 



Pressure Applied 1 Hour. 



31,51,84 


1:5 


5.75 


1.00 


0.875 


0.875 


2780* 


100 


Standard method of molding 


23 










0.845 


2920 


105 


Pressure, 2 lb. per sq. in. 


24 










0.824 


2830 


102 


5 lb. per sq. in. 


25 










0.839 


2950 


106 


" 10 lb. par sq. in. 


26 










0.834 


2880 


104 


" 25 lb. par sq. in. 


27 










0.821 


3120 


112 


" 50, !b. par sq. in. 


28 










0.810 


3190 


115 


100 1b. par sq. in. 


29 










0.781 


3790 


136 


200 lb. par sq. in. 


30 








Av. 


0.756 
0.820 


3470 
3100 


125 
112 


" 500 lb. per sq. in. 













Pressure Applied 4 Hours. 






31,51,84 


1:5 


5.75 


1.00 


0.875 


0.875 


2780* 


100 


Standard method of molding. 


23 










0.855 


2880 


104 


Pressure, 2 lb. per sq. in. 


24 












0.845 


2980 


107 


5 lb. per sq. in. 


25 












0.820 


3200 


115 


" 10 lb. per sq. in. 


26 












0.840 


2900 


104 


" 25 lb. per sq. in. 


27 












0.821 


2990 


108 


50 lb. per sq. in. 


28 












0.795 


3270 


118 


"" 100 lb. per sq. in. 


29 












0.767 


3350 


121 


200 lb. per sq. in. 


30 












0.750 


3680 


132 


" 500 lb. per sq. in. 










Av. 


0.819 


3120 


112 
















Pressure Applied 16 Hours 






31, 51, 84 


1:5 


5.75 


1.00 


0.875 


0.875 


2780* 


100 


Standard method of molding. 


23 










0.834 


3060 


110 


Pressure, 2 lb. per sq. in. 


24 










0.824 


2710 


97 


5 lb. per sq. in. 


25 










0.815 


2630 


95 


" 10 lb. per sq. in. 


26 










0.846 


2670 


96 


25 lb. per sq. in. 


27 










0.798 


3320 


119 


" 50 lb. per sq. in. 


28 










0.795 


3330 


120 


100 lb. per sq. in. 


29 










0.794 


3410 


123 


" 200 lb. per sq. in. 


30 








Av. 


0.766 
0.816 


3420 
3040 


123 

109 


" 500 lb. per sq. in. 



Grand Average of all Times of Application of Pressure (See Figs 13 to 16). 



1:5 


5.75 


1.00 


0.875 


0.875 
0.844 
0.834 
0.826 
0.834 
0.815 
0.802 
0.782 
0.756 


2780* 

3000 

2880 

2930 

2840 

3140 

3320 

3480 

3540 


100 
108 
104 
105 
102 
113 
119 
125 
127 



Standard method of molding. 
Pressure, 2 lb. per sq. in. 
5 lb. par sq. in. 

" 10 lb. per sq. in. 

" 25 lb. per sq. in. 

" • 50- lb. per sq. in. 

" 100 lb. per sq. in. 

" 200 lb. per sq. in. 

" 500 lb. par sq. in. 



Average of 15 tests made on different days, see Table 2. 



Effect of Vibration, Jigging and Pressure on Conckktk. 13 

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o/^ A/o/yy'/?^ 

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/Pe/o-f/ve Consistency 



£?0 



ISO 



FIG. 



5.— EFFECT OF CONSISTENCY ON THE STRENGTH OF JIGGED 
CONCRETE. 



Specimens molded by standard method and parallel sets jigged on machine shown in 
Fig. 2. Compression tests of 6 by 12-in. cylinders. Age 28 days. Data from Table 4. 

modulus 6.00 and over) are too coarse for this mix, consequently the con- 
crete strengths fall off. The extremely coarse mixtures cause a much 
greater reduction in the strength of the concrete made from crushed 
stone than from gravel. For this reason it is not proper to draw con- 
clusions from a comparison of average values from the two types of 
coarse aggregate. If we confine our attention to the ordinary range in 
aggregate grading (fineness, modulus 5.00 to 5.75) we find little difference 
in strength of concrete from the two materials. For these conditions the 
average strength with pebbles is 2550 lb. per sq. in. for the standard 
method of hand-puddling and 2190 after jigging; corresponding values 
for crushed stone are 2370 and 2190 lb. per sq. in. 

The tests of concrete setting under pressure are of interest in that 
they reveal the reason for increased strength due to this treatment. The 
concrete strength is increased due to the fact that some of the original 



U 



Structural Materials Research Laroratory. 




Jigged ' PO sec.. 

/OO drops per m/h. 

OJ/n. c/rop 

Average of /- 2 /-S^/^ono 7 

/-3M/xes - 



JO JS .SO .85 .90 <& /.OO /0 W //S t?0 /PS 
/xb/of/Ve Cons/'sfertcy 

FIG. 6.— EFFECT OF CONSISTENCY ON THE STRENGTH OF JIGGED 

CONCRETE. 

Each value is the average of 20 tests, 5 each from 4 different mixes in Table 4. 

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FIG. 7.— EFFECT OF SIZE OF AGGREGATE ON THE STRENGTH OF 

JIGGED CONCRETE. 
Compression tests of 6 by 12-in. cylinders. Age 28 days. Data from Table 5. 



Effect of Vibration, Jigging and Pressure on Concrete. 15 

mixing water is forced out. The higher the pressure, the more water is 
removed, hence the higher the strength. 

Attention is called to the unusual uniformity of the results of the 
tests in this series, as illustrated by the fact that in the diagrams the 
points fall on smooth curves ; in only a few instances is there an appreci- 
able deviation from this rule. 

Summary and Conclusions. 

The tests gave conclusive results on many phases of the effect of 

vibration, jigging and pressure. In some instances the effect is entirely 

different from what accepted opinion would suggest. Following is a 
brief summary : 

Effect of Puddling and Tamping. 

1. Varying the number of strokes from 12 to 50 on each 4-in. layer 
in the standard method of hand-puddling with a 5^-in. bar had little 
influence on the compressive strength of ordinary plastic concrete. 

2. In general, the tamping methods used gave lower strengths than 
hand-puddling. 

3. A tamper of large diameter for a given weight was less effective 
than one of small diameter. 

4. Increasing the thickness of the layer from 4 to 6 in. caused a 
falling-off in strength of about 12 per cent for tamped concrete. 

5. Tamping or puddling the first 4-in. layer only, caused a falling 
off in strength of 10 to 13 per cent. 

6. Striking the metal form with a steel bar after the completion of 
molding by standard method had no effect on the strength of concrete. 

7. The "standard" method of hand-puddling using 25 strokes with a 
5^-in. steel bar for each 4-in. layer of concrete in a 6 by 12-in. cylinder 
is recommended for laboratory tests of concrete. 

Effect of Vibration with Electric Hammer. 

8. Vibration of the specimen after molding by means of an electric 
hammer running at 1000 r. p. m. had little influence on the strength of the 
puddled concrete up to a period of about 30 seconds. If continued, there 
was a steady falling off in strength ; after 45 to 60 seconds the strength 
was only 90 per cent of that produced by the standard method of pud- 
dling. (Table 3, and Fig. 4.) 

Effect, of Jigging. 

9. In general, jigging in any manner with the apparatus used reduced 
the compressive strength of the concrete regardless of the height of drop, 
rate or duration of treatment. Exceptions were found in the dry mixes 
and those made of aggregates of the smaller sizes. (Tables 4 to 6; Fig. 
5 to 12.) 



16 



Structural Materials Research Laboratory. 



10. There was little difference in the effect of jigging due to the 
quantity of cement used. (Fig. 5.) 

11. In the very dry mixes the strength, due to jigging for 20 seconds, 
was increased about 25 per cent. (Fig. 5 and 6.) 

12. The wetter mixes (relative consistency 1.10 to 1.25) were reduced 
in strength 3 to 6 per cent by jigging. (Fig. 5 and 6.) 

.§<&00 



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'/??/s?. 



§ o I 1 i ' <-— 

400 4J& j:oo Jl^O £.00 6.SO 

FIG. 8.— EFFECT OF GRADING OF AGGREGATE ON THE STRENGTH OF 
JIGGED CONCRETE. 

Specimens molded by standard method and parallel sets jigged on machine shown in 
Fig. 2. Compression tests of 6 by 12-in. cylinders. 1:5 mix. Age, 28 days. All 
aggregate graded 0-1 ^4 in. Data from Table 5. 



13. Pebbles and crushed limestone as coarse aggregate gave essen- 
tially the same results in the jigging tests. (Fig. 8.) 

14. The concretes from the finer aggregates showed a material in- 
crease in strength with jigging in both 1:5 and 1:3 mixes. (Fig. 7.) 

15. For aggregate coarser than about Y%-m., jigging reduced in 
strength from 3 to 10 per cent. (Fig. 7.) 

16. The grading of the aggregates (for a given maximum size) had 
little influence on the effect of jigging. (Fig. 8.) 

17. The greater the drop the greater the reduction in strength for 1 : 5 
concrete. For a drop of J^-in. the strength was reduced 12 per cent. 
(Fig. 9.) 



Effect of Vibration, Jigging and Pressure on Concrete. 17 



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£h?/3 ■- /stc/p&s 



FIG . 9.— EFFECT OF HEIGHT OF DROP IN JIGGING TESTS. 
Compression tests of 6 by 12-in. cylinders. Age 28 days. Data from Table 6. 



%4000 

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FIG. 10.— EFFECT OF RATE OF JIGGING ON THE STRENGTH 

OF CONCRETE. 

Compression tests of 6 by 12-in. cylinders. 1:5 mix. Age 28 days. Data from Table 6. 



18 



Structural Materials Research Laboratory. 



1X^4000 

\ 

$ 3000 Y ■ i 

X 



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PS SO 7S /O0 /£f /SO /7S <POO 
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FIG. 11.— EFFECT OF DURATION OF JIGGING ON THE STRENGTH OF 

CONCRETE. 
Compression tests of 6 by 12-in. cylinders. 1:5 mix. Age 28 days. Data from Table 6. 




/OO c/zroyos per /7?//7. 
0.///7* c//"o/?. 



J 4 S 6 

/^?«f os* £hs7<?r<s>A2> £&£>/-<? J2?p/>7p -/potxrs 

FIG. 12.— EFFECT OF AGE OF CONCRETE BEFORE JIGGING. 
Compression tests of 6 by 12-in. cylinders. 1:5 mix. Age 28 days. Data from Table 6. 



Effkct of Vibration, Jigging and Pressure on Concrete. 



19 



18. The faster the rate of jigging the lower the strength of 1 : 5 con- 
crete. Using \y 2 -'m. aggregate at 150 r. p. m., the strength was reduced 
about 13 per cent. (Fig. 10.) 

19. The strength of 1 : 5 concrete fell off rapidly with the duration of 
jigging. After 2 to 3 minutes' jigging the strength was reduced about 20 
per cent as compared with standard method of hand-puddling. (Fig. 11.) 



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FIG. 13.— EFFECT OF PRESSURE ON THE STRENGTH OF CONCRETE. 

Compression tests of 6 by 12-in. cylinders. 1:5 mix. Age, 28 days. Pressure applied 
immediately after molding. Each point represents the average of 20 tests, 5 each 
from 4 different times of application of pressure ranging from 15 min. to 16 hr. 
Data from Table 7. 



20. Allowing the concrete to stand for a period of time before jig- 
ging, increased the strength to a slight extent. The maximum increase 
was found at 2 to 4 hr. (Fig. 12.) 

21. The application of a pressure of 1 lb. per sq. in. during the jig- 
ging process (equivalent to a head of 1 ft. of fresh concrete) gave the 
same strength as standard hand-puddling. (Fig. 9, 10 and 11.) 

22. Molding the cylinders by the standard method on the jigging 
table while it was in motion, gave the same strength as standard hand- 
puddling without jigging. (Table 6.) 



20 



Structural Materials Research Laboratory. 



Effect of Pressure. 

23. The compressive strength of concrete was increased by pressure 
applied immediately after molding. For pressure of 200 to 500 lb. per sq. 
in. the increase was 20 to 35 per cent. (Fig. 13.) 

n 40QO 

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14.— EFFECT OF DURATION OF PRESSURE ON THE STRENGTH OF 

CONCRETE. 

Compression tests of 6 by 12-in. cylinders. 1:5 mix. Age, 28 days. Pressure applied 

immediately after molding specimen. Each point represents the average of 45 

tests, 5 each from 9 different pressures ranging from 2 to 500 lb. per sq. in. 

Data from Table 7. 



24. The duration of pressure as between 15 min. and 16 hr. produced 
no difference in strength. (Fig. 14.) 

25. There was a steady reduction in the water-ratio of the concrete 
with the application of pressure. (Fig. 15.) 

26. The application of pressure increased the strength of concrete in 
accordance with the quantity of mixing water expelled. (Fig. 16.) 

27. The tests of "concrete subjected to pressure showed the usual 
relation between compressive strength and water-ratio. The strength is 



Effect of Vibration, Jigging and Pressure on Concrete. 



21 



increased because the water is expelled. In other words, pressure pro- 
duces a drier concrete, and consequently gives higher strength.* This 
makes it clear why the duration of pressure has no influence on the result. 

Further Discussion of Vibration, Jigging and Pressure Tests. 

The indications of the vibrations and jigging tests should not be mis- 
interpreted. The tests show that after the concrete is properly placed 




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FIG. 



15.— WATER-RATIO OF CONCRETE AFTER PRESSURE. 
Each point represents the average of 20 tests, 5 each from 4 different times of 
application of pressure. Data from grand average values in Table 7. 

these methods of treatment do no good and may be harmful if too severe 
or too long continued. However, there can be no doubt of the value of 
such methods for getting concrete into place in intricate forms and around 
reinforcing bars. The tests are of value in showing that this is the only 
desirable function of such treatments. The tests under Ref. No. 149 
(Table 2) show the ill effects of lack of compactness in the concrete. 



- *For effect of consistency on the strength of concrete, see Bulletin 1 referred to 
above; and "Effect of Time of Mixing Concrete," Proc, Am. Concrete Inst., 1918. 



22 



Structural Materials Research Laboratory. 



Here the strength was reduced 13 per cent due to failure to tamp or 
puddle the top 9 in. of the cylinder. It is impracticable to duplicate in a 
compression test piece the performance of air hammers and other similar 
methods of vibrating when used on reinforced concrete work. 

The tests show that with jigging high strength may be secured with 
drier mixes than would be feasible otherwise. It is a matter of common 
experience that concrete of drier consistency (and consequently higher 
strength) can be placed by means of jigging or vibration than would be 
possible by the usual methods. 

! 

sj SOOO 
i 

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7S 76 77 70 79 *&0 &/ .#P .6>J .&fi 6>S 

FIG. 16.— EFFECT OF QUANTITY OF MIXING WATER ON THE STRENGTH 

OF CONCRETE. 

Compression tests of 6 by 12-in. cylinders. Age, 28 days. Water-ratio determined 
after application of pressure. Each point represents the average of 45 tests, 5 
each from 9 different pressures. Data from grand average values in Table 7. 
The narrow range in water-ratio gives a straight line relation for these tests. 
The water-strength relation is represented by a curved line as shown in Bulletin 1, 
Structural Materials Research Laboratory. 






The roller method of finishing concrete roads, walks and floors is an 
interesting example of a combination of slight vibration and pressure 
accompanied by the removal of excess water. Transverse tests on con- 
crete made in this Laboratory showed a marked increase in strength of 
the rolled slabs as compared with similar slabs without rolling.* 



*See paper of A. N. Johnson, Proc. Am. Soc. Testing Mat., 1917, Part II, p. 378. 



Effi-xt of Vibration, Jigging and Prkssure on Concrete. 23 

It is clear from these tests that if tamping, vibration or pressure on 
fresh concrete are to be effective in increasing its strength three factors 
must be kept in mind : 

(1) We must take advantage of the fact that with these methods 
the concrete can be placed and finished drier than with ordinary 
methods. 

(2) Excess water which is brought to the surface must be 
removed. 

(3) We must take advantage of the fact that aggregate of a 
coarser grading may be used when such methods are employed than 
would be practicable otherwise. 

The advantages to be gained under (3) are due to the fact that up 
to a certain point a plastic mix can be secured with a smaller quantity of 
water if the aggregate is as coarse as practicable. Unless these pre- 
cautions are taken, tamping and vibration are of doubtful value. 



BIBLIOGRAPHY. 



Treatise on Limes, Cements, and Mortars, by O. A. Gillmore; 
Published by Van Nostrand, p. 225, and 239, 1863. 
Method of ramming concrete. 

Effect of Tamping (Discussion of Van Buren Street Bridge), by C. MacDonald; 
Trans. Am. Soc. Civil Eng., v. 20, p. 191, 1889. 

Cements tested for tensile strength fell below requirements and additional 
tamping brought strength above specifications. 

Tests of Cement at Watertown Arsenal, by J. E. Howard; 
Tests of Metals, 1903, p. 517, and 1904, p. 413. 
Cement Age, v. 2. p. 40, June, 1905. 

Studied effect of high pressures on cement paste in a confined space. 

Influence of Tamping on the Strength of Concrete, 
Eng. Rec, Sept. 22, 1906. 

Vibrating Table to Ensure Homogeneity in Cast Concrete Pieces, by P. B. Jagger; 
Indian and Eastern Engr., 1910. 
Cement Age, v. 11, p. 172, September, 1910. 

Oscillating and vibrating table used in London. 

Transported Concrete, by H. Burchartz; 
Beton u. Eisen, July 1, 1911. 

Tests show properties of concrete transported long distances as compared 
with ordinary concrete. 

Tests of Bond Between Concrete and Steel, by D. A. Abrams; 
Bull. 71, 111. Eng. Exp. Sta., 1913, p. 115. 

Compressive strength and bond resistance increased by pressures up to 100 
lb. per sq. in. during setting. 

Tests of Concrete Slabs to Determine Effect of Removing Excess Water Used in 

Mixing, by A. N. Johnson; 

Proc. Am. Soc. Testing Mat., v. 17, Part II, p. 378, 1917. 

Experimental studies carried out at Lewis Institute on roller method of 
finishing floors, roads, etc. Rolled slabs show marked increase in strength. 

Effect of Number of Strokes in Tamping Concrete, 
Baumaterialenkunde, v. 5, No. 8, 1917. 
Abs. Materials of Construction, by J. B. Johnson; 4th Ed., p. 629. 

Compressing Concrete Increases Its Strength, by F. P. McKibben; 
Eng. News-Rec, Dec. 5, 1918. 
Cement & Eng. News, v. 31, p. 22, July, 1919. 

Columns made by pouring successive layers and applying pressure gave 50% 

higher strength than ordinary concrete. 



24 Structural Materials Research Laboratory. 

Problems in Design and Construction of Reinforced Concrete Ships, by Wig and 
Hollister; 
Proc. Am. Concrete Inst., v. 18, p. 457, 1918. 

Air hammer used to settle concrete around steel. 

Pressing Out Mix Water Adds to Cement Mortar Strength, by C. T. Wiskocil; 
Eng. News-Rec, v. 83, p. 130, July 17, 1919. 

Tests made at University of California show that concrete molded under 
pressure gave high strengths. 

Effect of Rodding Concrete, by F. E. Giesecke; 
Eng. News-Rec, v. 82, p. 957, May 15, 1919. 
Concrete, v. 14, p. 196 and v. 15, p. 196 and 214, 1919. 
Eng. & Contr., v. 51, p. 543, May 21, 1919. 
Am. Archt., v. 116, p. 467, Oct. 1, 1919. 
Can. Engr., v. 37, p. 217, Aug. 14, 1919. 

Tests made at University of Texas. Rodding increased strength of concrete. 

Effect of Vibration, Jigging and Pressure on Fresh Concrete, by D. A. Abrams; 
Proc. Am. Concrete Inst., v. 15, p. 63, 1919. 
Bull. 3, Structural Materials Research Lab., 1920. 
Jl. Eng. Inst, of Canada, v. 3, p. 181, April, 1920. 
Mun. Jl. & Public Works, v. 48, p. 43, Jan. 31, 1920. 

Method of Construction of Concrete Ships, by R. J. Wig; 
Proc. Am. Concrete Inst., v. 15, p. 266, 1919. 

Describes use of air hammer for vibrating forms. 

Goodlet Vibrator. 

U. S. Patent 1,340,860, May 18, 1920. 

Effect of Rodding Concrete, by F. E. Giesecke; 

Proc. Am. Soc. Testing Mat., June 22, 1920. 

Concrete, v. 16, p. 102, February, 1920. 

Eng. & Contr., v. 54, p. 184, Aug. 25, 1920. 

Eng. World, v. 17, p. 89, August, 1920. 

Can. Engr., v. 38, p. 118, Jan. 8. 1920. 

Tests made at University of Texas; continuation of earlier work; graph 
shows comparison of Abrams' curve with strengths of rodded concrete; 
water-ratios based on quantity of water in concrete before and after rodding. 

Influence of Jarring on the Strength of Concrete, by H. Schafer; 
Prometheus, v. 31, p. 140, Jan. 31, 1920. 

Experiments carried out in the Saxon Mech. -Technical Experimental Inst., 
Dresden, show that a slight jarring before setting begins has favorable effect 
on strength; during setting period its influence varied; after cement is hard- 
ened, no apparent effect. 

Effect of Ramming on Strength of Mortars (Long-Time Tests of Portland Cement, 
Hydraulic Lime and Volcanic Ashes), by I. Hiroi; 
Jl. Coll. Eng. Tokyo Imperial University, v. 10, p. 155-72, 1920. 

Birkenhead-Alwen Water Supply, 

Concrete & Const. Eng., Oct., 1921, p. 643. 

Concrete blocks for dam consolidated by vibrating table and air hammer. 

Effect of Vibration in Molding Concrete, 

Concrete & Const. Eng., Aug., 1921, p. 535. 

Block vibrated with pneumatic hammer and strength compared with un- 
vibrated block. 

Tests on Molding of Concrete Under Pressure, by H. M. Nelson; 
Eng. Rec, v. 89, p. 21, July 6, 1922. 

Effect of pressures up to 5,000 lb. per sq. in. and of curing in air, steam 
and water. 

Density of Concrete, by F. E. Giesecke; ■ 

Proc. Am. Soc. Testing Mat., v. 22, Part II, 1922. 

Concrete Ships Constructed by U. S. Shipping Board, by W. R. Harper; 
Proc. Am. Concrete Inst., v. 18, p. 97, 1922. 

Describes use of air hammer for vibrating forms. 



LIST OF PUBLICATIONS OF THE 
STRUCTURAL MATERIALS RESEARCH LABORATORY 



Circular 1.— Colorimetric Test for Organic Impurities in Sands, by Duff A. 
Abrams and Oscar E. Harder (1917). Out of Print. 

(For a more recent discussion of this subject see, "Abrams-Harder Field Test 
for Organic Impurities in Sands," Proc. Am. Soc. Testing Mat., 1919, Part I; 
also "Tentative Method of Test for Organic Impurities in Sands for Con- 
crete," Proc. Am. Soc. Testing Mat., 1921.) 

Bulletin 1. — Design of Concrete Mixtures, by Duff A. Abrams (1918). 

Bulletin 2. — Effect of Curing Condition on the Wear and Strength of Concrete, 
by Duff A. Abrams (1919). 

Reprinted from the Proc. Am. Railway Eng. Assn., Vol. 20, 1919. 

Bulletin 3. — Effect of Vibration, Jigging and Pressure on Fresh Concrete, by 
Duff A. Abrams (1919). 

Reprinted from the Proc. Am. Concrete Inst., Vol. XV, 1919. 

Bulletin 4. — Effect of Fineness of Cement, by Duff A. Abrams (1919). 

Reprinted from the Proc. Am. Soc. Testing Mat., Vol. XIX, Part II, 1919. 

Bulletin 5. — Modulus of Elasticity of Concrete, by Stanton Walker (1920). 

Reprinted from the Proc. Am. Soc. Testing Mat.. Vol. XIX. Part II. 1919. 

Bulletin 6. — Effect of Storage of Cement, by Duff A. Abrams (1920). 

Bulletin 7. — Effect of Tannic Acid on the Strength of Concrete, by Duff A. 
Abrams (1920). 

Reprinted from the Proc. Am. Soc. Testing Mat., Vol. XX, Part I, 1920. 

Bulletin 8. — Effect of Hydrated Lime and Other Powdered Admixtures in 
Concrete, by Duff A. Abrams (1920). 

Reprinted from the Proc. Am. Soc. Testing Mat., Vol. XX, Part II, 1920. 

Bulletin 9. — Quantities of Materials for Concrete, by Duff A. Abrams and 
Stanton Walker (1921). 

Bulletin 10.— Wear Test of Concrete, by Duff A. Abrams (1921). 

Reprinted from Proc. Am. Soc. Testing Mat., Vol. 21, 1921. 

Bulletin 11. — Flexural Strength of Plain Concrete, by Duff A. Abrams (1922). 

Reprinted from the Proc. Am. Concrete Inst. Vol. XVIII. 1922. 



